Modern mobile stations, sometimes referred to as mobile terminals (MTs) or user equipment (UE), are often capable of connecting to and communicating with two or more different types of radio access networks. One example is a dual-mode mobile terminal capable of connecting to a second generation (2G) radio access network, such as the Global System for Mobile communication (GSM), Digital Advanced Mobile Phone System (D-AMPS), or Pacific Digital Cellular system (PDC), as well as to a third generation (3G) radio access network, such as Universal Mobile Telecommunication System (UMTS) Terrestrial Radio Access Network (UTRAN). Other radio technologies, such as Bluetooth or 802.11, may also be used. An environment that enables access to more than one radio access technology (RAT) is called a multi-access environment.
In GSM/GPRS and WCDMA systems, mobility management is related to the state of the mobile station. In general, when the mobile station is “attached” to a network, it can be in either an idle/ready state in which it is not involved in an active connection, e.g. a communication with another subscriber, or in an connected/active mode in which the mobile terminal is engaged in active connection, e.g., communicating with another subscriber, and receiving service from the network. Although the states of the mobile station may have different labels in different systems, the term “idle” mobile station is used to cover a mobile station in any state in which the mobile station is powered-on but is not actively participating in a communication. During an idle state, the mobile station may select, register with, and “camp on” a cell in order to obtain service when desired by the mobile subscriber or when an incoming call is made to the mobile subscriber. Camping is the mode an idle mobile station adopts after it registers with a cell. Non-limiting examples of a mobile station being in an idle state where it selects the cell to receive service includes an idle state, a ready state, a stand by state, a CELL_FACH state, a CELL_PCH state, and a URA_PCH state.
In the idle state, a mobile station reads system information (all or only part) broadcast by various cells, including the cell in which the mobile terminal is currently located or registered and neighboring cells, to determine whether to select another cell to camp on. When an idle mobile station decides to select another cell to camp on, that process is sometimes referred to as cell re-selection. Once a cell re-selection occurs, the network will receive a location update message from the mobile terminal and update the stored location information, (e.g., cell, location area, routing area, etc.), which may be used to page the mobile station.
Ideally, network operators would prefer to have total flexibility in directing or steering mobile subscribers between networks using different radio access technologies, e.g., to divide the subscribers in different service categories like “gold/silver” subscriptions. This might mean that some mobile stations might camp on a UMTS-based cell while in an idle state as long as there UMTS coverage. In contrast, idle mobile stations of less-preferred subscribers are directed to camp on a GSM/GPRS cell. These less preferred subscribers may still have the possibility to move to a UMTS cell when requesting certain services.
In order to provide satisfactory service to mobile subscribers and to maximize the capacity of a mobile communications network, it is important to balance the overall network load amongst the various cells within that network. It would be desirable to direct or steer mobile terminals from their respective current cells, if the loads in those current cells exceed a particular threshold, to a neighboring or overlapping cell with a lower load. Switching active mobile stations with an active connection between cells requires substantial signaling, particularly when the switch is made from a cell in one radio access technology system to another, e.g., WCDMA to GSM. Moving active subscribers also requires that the connection between the mobile terminal and the network be maintained during the entire time that the inter-system change is taking place in order to ensure that the promised quality of service is maintained for that active connection. This consumes considerable resources in both the core and radio networks.
A better solution for satisfying subscriber preferences and network operator preferences, providing subscription services, and accomplishing network management type functions like load redistribution and others is to dynamically distribute or “steer” idle mobile stations to a particular cell or area. For example, idle mobile stations may be steered to less loaded load monitoring areas, (e.g., like cells, location areas, etc.), in the same or different networks.
In one non-limiting example, mobile stations are distributed between load monitoring areas when they are in a state where the mobile station selects a cell to receive service based on one or more parameters provided by one or both of a first broadcast signal in a cell in a first load monitoring area or a second broadcast signal in a cell in a second load monitoring area. The load associated with the first area where one or more mobile stations are currently camped is determined. To reduce the load for the first area, e.g., the load monitoring area load is too high or otherwise exceeds a threshold, adjustment of one or more parameters in one or both of the broadcast messages is initiated in order to steer some mobile stations to camp on the second load monitoring area (which is preferably less loaded).
The first and second load monitoring may be cells, location areas, routing areas, or service areas. The adjustment may be initiated based upon load information from a core network node, a radio access network node, or from a central server. In a preferred, non-limiting example application, the first load monitoring area is associated with a first mobile communications network that offers a first set of services, and the second load monitoring area is associated with the second mobile communications network that offers a second set of services. Of course, this methodology can be extended to third and additional communications networks, particularly when the subscribed services can be obtained from an additional network.
The first mobile communications network may employ a first radio access technology, and the second mobile communications network may employ a second different radio access technology. For example, the first mobile communications network may be a second generation-based network, and the second communications network may be a third generation-based network. The first and second set of services may be different or the same.
The adjustment instruction may be based on an exchange of load information between a first radio access network node in the first mobile communications network, and a second radio access network node in the second mobile communications network. Alternatively, the adjustment instruction may be based on load information from a core network node, or it can be based on load information from a central server.
As an example implementation of broadcast parameter adjustment, an offset may be applied to a broadcast parameter. An offset parameter may be added to or subtracted from a signal that is measured by the mobile station for a cell selection procedure or a cell re-selection procedure. In order to avoid unnecessary battery drain in idle mobiles, the rate of change at which the broadcast parameters are changed may be controlled.